When excavating long trenches with a digging or trenching machine, the geological formation through which the trench extends often changes from highly frangible dirt, to other unconsolidated formations, and then to rock. There are digging implements made especially for penetrating dirt-like formations, and there are other radically different digging teeth especially adapted for forming a trench through rock. For this reason, it would be advantageous to be able to readily substitute a rock-type digging tooth for a dirt-type digging tooth, and vice versa, depending upon the characteristics of the geological formation through which the trench extends.
Swisher U.S. Pat. No. 4,335,921 teaches a cutting head which can be placed within a box wherein the box is designed to receive a cylindrical shank of a digging tooth. Means are provided by which the digging tooth is rendered non-rotatable. College, et al U.S. Pat. No. 4,346,934 also provides means by which the digging teeth are rendered non-rotatable.
The present invention constitutes an improvement over the prior art by the provision of a combination digging tooth and support box wherein the support box and digging tooth cooperate to proclude rotation of the digging tooth, yet the support box bore can also receive rock-type bits of the rotatable type when it is deemed desirable to do so.